Guideline for Exam 642-642
Exam Number
642-642
Associated Certifications
CCIP, CCVP
Duration
90 minutes (45-55 questions)
Available Languages
English
Exam Topics
IP QoS Fundamentals
? Given a description of a converged network, identify problems that could lead to poor quality of service and explain how the problems might be resolved
? Define the term Quality of Service (QoS) and identify and explain the key steps to implementing QoS on a converged network
IP QoS Components
? List and explain the models for providing Quality of Service on a network
? Explain the purpose and function of the DiffServ model
? Describe the basic format of and explain the purpose of the DSCP field in the IP header
? Define and explain the different per hop behaviors used in DSCP
? Explain the interoperability between DSCP-based and IP-precedence-based devices in a network
? Given a list of QoS actions, correctly match the QoS actions to mechanisms for implementing QoS and identify where in a network the different QoS mechanisms are commonly used
Modular QoS CLI and Auto-QoS
? Given a network requiring QoS, explain how to implement a QoS policy using MQC
? Explain how AutoQoS is used to implement QoS policy
Classification and Marking
? Explain how link layer and network layer markings are used to define service classes and the different applications represented by each of these service classes
? Given a network and a description of QoS issues, use MQC CLI commands to classify packets
? Given a network and a description of QoS issues, use class-based marking to assign packets to a specific service class
? Describe the function of Network Based Application Recognition
? Describe the purpose of pre-classification to support QoS in various VPN (IPSEC, GRE, L2TP) configurations
? Describe QoS trust boundaries and their significance in LAN based classification and marking
? Identify the different classification and marking options available on Cisco L2 and L3 switching platforms
Congestion Management Methods
? List and explain the different queuing algorithms
? Explain the components of hardware and software queuing systems on Cisco routers and how they are effected by tuning and congestion
? Describe the benefits and drawbacks of using WFQ to implement QoS
? Explain the purpose and features of Class-Based WFQ (CBWFQ)
? Explain the purpose and features of Low Latency Queuing (LLQ)
? Identify the Cisco IOS commands required to configure and monitor LLQ on a Cisco router
? Describe and explain the different queuing capabilities available on the Cisco Catalyst 2950 Switch
Congestion Avoidance Methods
? Describe the drawbacks tail drop as a congestion control mechanism
? Describe the elements of a RED traffic profile
? Describe Weighted Random Early Detection and how it can be used to prevent congestion
? Identify the Cisco IOS commands required to configure and monitor DSCP-based CB-WRED
? Explain how ECN interacts with WRED in Cisco IOS
Traffic Policing and Shaping
? Describe the purpose of traffic conditioning using traffic policing and traffic shaping and differentiate between the features of each
? Explain how network devices measure traffic rates using single rate or dual rate, single or dual token bucket mathematical models
? Identify the Cisco IOS commands required to configure and monitor single rate and dual rate CB-Policing
? Identify the Cisco IOS commands required to configure and monitor percentage based CB-Policing
? Explain how the two rate limits, average rate and peak rate, can be used to rate limit traffic
? Identify the Cisco IOS commands required to configure and monitor CB-Shaping
? Identify the Cisco IOS commands required to configure and monitor Frame Relay adaptive CB-Shaping on Frame Relay interfaces
Link Efficiency Mechanisms
? Explain the various link efficiency mechanisms and their function
? Identify the Cisco IOS commands required to configure and monitor CB header compression
? Given a list of link speeds and a specific delay requirement, determine the proper fragment size to use at each link speed and identify the typical delay requirement for VoIP packets
? Identify the Cisco IOS commands required to configure and monitor Multilink PPP with Interleaving
? Identify the Cisco IOS commands required to configure and monitor FRF.12
QoS Best Practices
? Explain the QoS requirements of the different application types
? List typical enterprise traffic classes then identify the delay, jitter, packet loss and bandwidth requirements of each traffic class
? Explain the best practice QoS implementations and configurations within the campus LAN
? Explain the best practice QoS implementations and configurations on the WAN customer edge (CE) and provider edge (PE) routers
